Code-division multiple access: Difference between revisions

Revision as of 16:33, 1 May 2021

Revision as of 17:24, 1 May 2021

Line 13:

In these schemes, the message is modulated on a longer spreading sequence, consisting of several chips (0es and 1es). Due to their very advantegous auto- and crosscorrelation characteristics, these spreading sequences are also used for radar applications since many decades, where they are called Barker-Codes (with a very short sequence length of typically 8 to 32).

For space based communication applications, it is also used since many decades, due to the large pathloss and Doppler-shift caused by the satellite motion. Typically in those applications, neither FDMA nor TDMA is used as a single modulation, due to this effect. CDMA is often used with BPSK in its simplest form, but can be combined with any modulation scheme like in advanced cases QAM or OFDM, which typically makes it very robust and efficient. Other schemes use subcarriers based on binary offset carrier (BOC), which is inspired by Manchester codes and enable are larger distancegap between the center frequency and the subcarriers, which is not the case for OFDM subcarriers.

==History==